The present invention relates to a compound blazed optical phase grating.
Such a grating is described in an article by H. Dammann entitled "From prism-prism via grating-prism to grating-grating compounds" (Applied Optics, Vol. 19, No. 14, 15 July 1980, pages 2276 to 2278). Blazed phase gratings of the type described in this article have substantially sawtooth-shaped profiles. These gratings diffract light into specific diffraction orders with a high efficiency. The diffraction order depends, inter alia, on the inclination of the groove walls. How the remainder of the light is distributed over the other diffraction orders is generally irrelevant.
However, once the grating parameters are chosen, gratings of this type do not diffract light with a high efficiency into other diffraction orders. Once the diffraction order is determined by the selected grating profile, it cannot be varied.